#include <stdio.h>
#define pi 3.1415
int main(int argc, char const *argv[])
{
    float r;
    printf("请输入圆的半径r:");
    scanf("%f", &r);
    printf("r=%f\n", r);
    printf("圆的周长为%f\n", 2 * pi * r);
    printf("圆的面积为%f", pi * r * r);
}